Patent specification WO2015114440 describes the prior art and proposes such a system comprising a floating platform on the surface of a body of water (lake or sea), equipped with a lift system which allows weights to be raised and lowered one by one in order to store and generate electricity by means of an electric motor/generator. The weights are stored in the upper position by being attached to one or more floats, at least part of which is located at the surface when said weights are stored in the upper position. In the lower position, the weights are set down on the bottom of the body of water. Before and after having been driven by or having driven the lift system, the weights can be attached to and then detached from the lift system by using underwater robots equipped with an articulated arm.
Since the platform and at least part of the floating component of the weights are positioned at the surface, they are subjected to surface winds and currents which result in very substantial anchoring and stabilisation costs, particularly if the system has to be dimensioned to withstand major storms and a heavy swell.
When the sea is rough, the movements, in particular the vertical oscillation movements, which the platform and to a lesser extent the weights stored in the upper position undergo may have an impact on the lift system, in particular on the cable, and disrupt the operations involved in attaching/detaching the weights to/from the cable of the lift system. The vertical oscillation movements of the weights attached to the lift system may also prevent the weights from being set down gently on the bottom of the body of water and so result in higher costs for said weights or reduce the life thereof.
The present invention proposes inter alia reducing or eliminating the exposure of the platform and the weights stored in the upper position to surface wind and currents and reducing or eliminating platform movements and their impact on the operations involved in attaching/detaching the weights and setting them down on the bottom of the body of water.
According to the invention, the weights in the upper energy storage position and the lift platform are stabilised at a depth such that the effect of the wind and currents are greatly reduced.